A capsule for inspecting conduit interiors has been blown with high stability using spiral air flow. Maintaining stability increases both the accuracy and workability of inspection process in the telecommunication industry. To elucidate this stabilization, the model of the capsule motion in both turbulent and spiral flows has been investigated from a fluid dynamics viewpoint. In a turbulent pipe flow, the air flow is disturbed by the irregularly-rotating wake in the rear of the capsule. This leads to an increase in capsule and air flow instability which in turn makes completion of the inspection process impossible. However, the steep velocity distribution of the ordered spiral airflow positions the wake to the side of the pipe axis. Thus the downstream flow increases its radial pressure gradient resulting in effective capsule stabilization. This capsule stabilization was achieved by synergism between the spiral air flow and capsule.